diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index a0a7091..6fa1ab4 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use CodeIgniter\CodingStandard\CodeIgniter4;
 use Nexus\CsConfig\Factory;
 use PhpCsFixer\Finder;
@@ -20,8 +22,8 @@
     ]);
 
 $overrides = [
-    // 'declare_strict_types' => true,
-    // 'void_return'          => true,
+    'declare_strict_types' => true,
+    'void_return'          => true,
 ];
 
 $options = [
diff --git a/UPGRADING.md b/UPGRADING.md
index 9a59d9a..05203c0 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -1,5 +1,11 @@
 # Upgrade Guide
 
+## Version 2.2.0 to 2.3.0
+
+* The minimum required version of CodeIgniter is now `4.3` and PHP `8.2`.
+* All source files now declare `strict_types=1`.
+* `BaseHandler` methods `set()`, `forget()`, `flush()`, and `persistPendingProperties()` now have `void` return types. Any custom handler extending `BaseHandler` must update its method signatures to include `: void`.
+
 ## Version 1 to 2
 ***
 
diff --git a/composer.json b/composer.json
index a51f78d..9c878d6 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "codeigniter4/devkit": "^1.3",
-        "codeigniter4/framework": "^4.2.3"
+        "codeigniter4/framework": "^4.3"
     },
     "minimum-stability": "dev",
     "prefer-stable": true,
diff --git a/docs/limitations.md b/docs/limitations.md
index 9822665..d59c9c7 100644
--- a/docs/limitations.md
+++ b/docs/limitations.md
@@ -10,9 +10,9 @@ The following are known limitations of the library:
 2. **Deferred writes (`deferWrites => true`)**: All settings are batched and written to storage at the end of the request
    (during the `post_system` event). This minimizes the number of database queries and file writes, improving performance.
    However, there are important considerations:
-   - Write operations will not appear in CodeIgniter's Debug Toolbar, since the `post_system` event executes after toolbar data collection.
-   - If the request terminates early (fatal error, `exit()`, etc.) before `post_system`, pending writes are lost.
-   - Write failures are logged but handled silently - no exceptions are thrown back to the calling code.
+    - Write operations will not appear in CodeIgniter's Debug Toolbar, since the `post_system` event executes after toolbar data collection.
+    - If the request terminates early (fatal error, `exit()`, etc.) before `post_system`, pending writes are lost.
+    - Write failures are logged but handled silently - no exceptions are thrown back to the calling code.
 
 3. **First-level property access only**: You can only access the first level of a config property directly. In most config classes
    this is not an issue, since properties are simple values. However, some config files (like `Database`) contain properties that
diff --git a/psalm.xml b/psalm.xml
index 6b0fb24..142455e 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <psalm
-    phpVersion="8.1"
+    phpVersion="8.2"
     errorLevel="7"
     resolveFromConfigFile="true"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
diff --git a/rector.php b/rector.php
index 3eec8d9..be7e034 100644
--- a/rector.php
+++ b/rector.php
@@ -42,7 +42,13 @@
 use Rector\ValueObject\PhpVersion;
 
 return static function (RectorConfig $rectorConfig): void {
-    $rectorConfig->sets([SetList::DEAD_CODE, LevelSetList::UP_TO_PHP_74, PHPUnitSetList::PHPUNIT_80]);
+    $rectorConfig->sets([
+        SetList::DEAD_CODE,
+        LevelSetList::UP_TO_PHP_82,
+        PHPUnitSetList::PHPUNIT_CODE_QUALITY,
+        PHPUnitSetList::PHPUNIT_100,
+    ]);
+
     $rectorConfig->parallel();
     // The paths to refactor (can also be supplied with CLI arguments)
     $rectorConfig->paths([
@@ -65,7 +71,7 @@
     }
 
     // Set the target version for refactoring
-    $rectorConfig->phpVersion(PhpVersion::PHP_74);
+    $rectorConfig->phpVersion(PhpVersion::PHP_82);
 
     // Auto-import fully qualified class names
     $rectorConfig->importNames();
diff --git a/src/Commands/ClearSettings.php b/src/Commands/ClearSettings.php
index 73c6bcc..dcde19f 100644
--- a/src/Commands/ClearSettings.php
+++ b/src/Commands/ClearSettings.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
@@ -12,7 +14,7 @@ class ClearSettings extends BaseCommand
     protected $name        = 'settings:clear';
     protected $description = 'Clears all settings from persistent storage.';
 
-    public function run(array $params)
+    public function run(array $params): void
     {
         $config   = config('Settings');
         $handlers = $this->getHandlerNames($config);
diff --git a/src/Config/Services.php b/src/Config/Services.php
index f4fca95..bf77f18 100644
--- a/src/Config/Services.php
+++ b/src/Config/Services.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Config;
 
 use CodeIgniter\Config\BaseService;
diff --git a/src/Config/Settings.php b/src/Config/Settings.php
index face85a..4165a9f 100644
--- a/src/Config/Settings.php
+++ b/src/Config/Settings.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Config;
 
 use CodeIgniter\Config\BaseConfig;
diff --git a/src/Database/Migrations/2021-07-04-041948_CreateSettingsTable.php b/src/Database/Migrations/2021-07-04-041948_CreateSettingsTable.php
index eb45235..26a4301 100644
--- a/src/Database/Migrations/2021-07-04-041948_CreateSettingsTable.php
+++ b/src/Database/Migrations/2021-07-04-041948_CreateSettingsTable.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Database\Migrations;
 
 use CodeIgniter\Database\Forge;
@@ -8,7 +10,7 @@
 
 class CreateSettingsTable extends Migration
 {
-    private Settings $config;
+    private readonly Settings $config;
 
     public function __construct(?Forge $forge = null)
     {
@@ -18,7 +20,7 @@ public function __construct(?Forge $forge = null)
         parent::__construct($forge);
     }
 
-    public function up()
+    public function up(): void
     {
         $this->forge->addField('id');
         $this->forge->addField([
@@ -51,7 +53,7 @@ public function up()
         $this->forge->createTable($this->config->database['table'], true);
     }
 
-    public function down()
+    public function down(): void
     {
         $this->forge->dropTable($this->config->database['table']);
     }
diff --git a/src/Database/Migrations/2021-11-14-143905_AddContextColumn.php b/src/Database/Migrations/2021-11-14-143905_AddContextColumn.php
index 9bf7fe2..27a0fb3 100644
--- a/src/Database/Migrations/2021-11-14-143905_AddContextColumn.php
+++ b/src/Database/Migrations/2021-11-14-143905_AddContextColumn.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Database\Migrations;
 
 use CodeIgniter\Database\Forge;
@@ -8,7 +10,7 @@
 
 class AddContextColumn extends Migration
 {
-    private Settings $config;
+    private readonly Settings $config;
 
     public function __construct(?Forge $forge = null)
     {
@@ -18,7 +20,7 @@ public function __construct(?Forge $forge = null)
         parent::__construct($forge);
     }
 
-    public function up()
+    public function up(): void
     {
         $this->forge->addColumn($this->config->database['table'], [
             'context' => [
@@ -30,7 +32,7 @@ public function up()
         ]);
     }
 
-    public function down()
+    public function down(): void
     {
         $this->forge->dropColumn($this->config->database['table'], 'context');
     }
diff --git a/src/Handlers/ArrayHandler.php b/src/Handlers/ArrayHandler.php
index b1a2320..aee8f26 100644
--- a/src/Handlers/ArrayHandler.php
+++ b/src/Handlers/ArrayHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Handlers;
 
 use CodeIgniter\Events\Events;
@@ -54,17 +56,17 @@ public function get(string $class, string $property, ?string $context = null)
         return $this->getStored($class, $property, $context);
     }
 
-    public function set(string $class, string $property, $value = null, ?string $context = null)
+    public function set(string $class, string $property, $value = null, ?string $context = null): void
     {
         $this->setStored($class, $property, $value, $context);
     }
 
-    public function forget(string $class, string $property, ?string $context = null)
+    public function forget(string $class, string $property, ?string $context = null): void
     {
         $this->forgetStored($class, $property, $context);
     }
 
-    public function flush()
+    public function flush(): void
     {
         $this->general  = [];
         $this->contexts = [];
@@ -189,7 +191,7 @@ protected function setupDeferredWrites(bool $enabled): void
         $this->deferWrites = $enabled;
 
         if ($this->deferWrites) {
-            Events::on('post_system', [$this, 'persistPendingProperties']);
+            Events::on('post_system', $this->persistPendingProperties(...));
         }
     }
 }
diff --git a/src/Handlers/BaseHandler.php b/src/Handlers/BaseHandler.php
index 696f854..95f96fd 100644
--- a/src/Handlers/BaseHandler.php
+++ b/src/Handlers/BaseHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Handlers;
 
 use RuntimeException;
@@ -26,11 +28,9 @@ abstract public function get(string $class, string $property, ?string $context =
      *
      * @param mixed $value
      *
-     * @return void
-     *
      * @throws RuntimeException
      */
-    public function set(string $class, string $property, $value = null, ?string $context = null)
+    public function set(string $class, string $property, $value = null, ?string $context = null): void
     {
         throw new RuntimeException('Set method not implemented for current Settings handler.');
     }
@@ -41,11 +41,9 @@ public function set(string $class, string $property, $value = null, ?string $con
      * Not all Handlers will support writing values.
      * Must throw RuntimeException for any failures.
      *
-     * @return void
-     *
      * @throws RuntimeException
      */
-    public function forget(string $class, string $property, ?string $context = null)
+    public function forget(string $class, string $property, ?string $context = null): void
     {
         throw new RuntimeException('Forget method not implemented for current Settings handler.');
     }
@@ -53,11 +51,9 @@ public function forget(string $class, string $property, ?string $context = null)
     /**
      * All handlers MUST support flushing all values.
      *
-     * @return void
-     *
      * @throws RuntimeException
      */
-    public function flush()
+    public function flush(): void
     {
         throw new RuntimeException('Flush method not implemented for current Settings handler.');
     }
@@ -65,11 +61,9 @@ public function flush()
     /**
      * All handlers that support deferWrites MUST support this method.
      *
-     * @return void
-     *
      * @throws RuntimeException
      */
-    public function persistPendingProperties()
+    public function persistPendingProperties(): void
     {
         throw new RuntimeException('PersistPendingProperties method not implemented for current Settings handler.');
     }
diff --git a/src/Handlers/DatabaseHandler.php b/src/Handlers/DatabaseHandler.php
index 8b97ab7..a5701a4 100644
--- a/src/Handlers/DatabaseHandler.php
+++ b/src/Handlers/DatabaseHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Handlers;
 
 use CodeIgniter\Database\BaseBuilder;
@@ -18,12 +20,12 @@ class DatabaseHandler extends ArrayHandler
     /**
      * The DB connection for the Settings.
      */
-    private BaseConnection $db;
+    private readonly BaseConnection $db;
 
     /**
      * The Query Builder for the Settings table.
      */
-    private BaseBuilder $builder;
+    private readonly BaseBuilder $builder;
 
     /**
      * Array of contexts that have been stored.
@@ -32,7 +34,7 @@ class DatabaseHandler extends ArrayHandler
      */
     private array $hydrated = [];
 
-    private Settings $config;
+    private readonly Settings $config;
 
     /**
      * Stores the configured database table.
@@ -74,11 +76,9 @@ public function get(string $class, string $property, ?string $context = null)
      *
      * @param mixed $value
      *
-     * @return void
-     *
      * @throws RuntimeException For database failures
      */
-    public function set(string $class, string $property, $value = null, ?string $context = null)
+    public function set(string $class, string $property, $value = null, ?string $context = null): void
     {
         if ($this->deferWrites) {
             $this->markPending($class, $property, $value, $context);
@@ -137,10 +137,8 @@ private function persist(string $class, string $property, $value, ?string $conte
     /**
      * Deletes the record from persistent storage, if found,
      * and from the local cache.
-     *
-     * @return void
      */
-    public function forget(string $class, string $property, ?string $context = null)
+    public function forget(string $class, string $property, ?string $context = null): void
     {
         $this->hydrate($context);
 
@@ -175,10 +173,8 @@ private function persistForget(string $class, string $property, ?string $context
     /**
      * Deletes all records from persistent storage, if found,
      * and from the local cache.
-     *
-     * @return void
      */
-    public function flush()
+    public function flush(): void
     {
         $this->builder->truncate();
 
@@ -228,10 +224,8 @@ private function hydrate(?string $context): void
      * Persists all pending properties to the database.
      * Called automatically at the end of request via post_system
      * event when deferWrites is enabled.
-     *
-     * @return void
      */
-    public function persistPendingProperties()
+    public function persistPendingProperties(): void
     {
         if ($this->pendingProperties === []) {
             return;
diff --git a/src/Handlers/FileHandler.php b/src/Handlers/FileHandler.php
index dec21eb..ec6d65c 100644
--- a/src/Handlers/FileHandler.php
+++ b/src/Handlers/FileHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings\Handlers;
 
 use CodeIgniter\Settings\Config\Settings;
@@ -22,9 +24,9 @@ class FileHandler extends ArrayHandler
     /**
      * Base path where settings files are stored.
      */
-    private string $path;
+    private readonly string $path;
 
-    private Settings $config;
+    private readonly Settings $config;
 
     /**
      * Stores the configured file path and ensures it exists.
@@ -74,11 +76,9 @@ public function get(string $class, string $property, ?string $context = null)
      *
      * @param mixed $value
      *
-     * @return void
-     *
      * @throws RuntimeException For file write failures
      */
-    public function set(string $class, string $property, $value = null, ?string $context = null)
+    public function set(string $class, string $property, $value = null, ?string $context = null): void
     {
         $this->hydrate($class, $context);
 
@@ -101,11 +101,9 @@ public function set(string $class, string $property, $value = null, ?string $con
      * Deletes the record from persistent storage, if found,
      * and from the local cache.
      *
-     * @return void
-     *
      * @throws RuntimeException For file write failures
      */
-    public function forget(string $class, string $property, ?string $context = null)
+    public function forget(string $class, string $property, ?string $context = null): void
     {
         $this->hydrate($class, $context);
 
@@ -128,11 +126,9 @@ public function forget(string $class, string $property, ?string $context = null)
      * Deletes all settings files from persistent storage
      * and clears the local cache.
      *
-     * @return void
-     *
      * @throws RuntimeException For file deletion failures
      */
-    public function flush()
+    public function flush(): void
     {
         // Delete all .php files in main directory (null context files)
         $files = glob($this->path . '*.php', GLOB_NOSORT);
diff --git a/src/Helpers/setting_helper.php b/src/Helpers/setting_helper.php
index 1282130..2b9cc2a 100644
--- a/src/Helpers/setting_helper.php
+++ b/src/Helpers/setting_helper.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use CodeIgniter\Settings\Settings;
 
 if (! function_exists('setting')) {
diff --git a/src/Settings.php b/src/Settings.php
index 0e0d62c..9894177 100644
--- a/src/Settings.php
+++ b/src/Settings.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Settings;
 
 use CodeIgniter\Config\BaseConfig;
@@ -74,10 +76,8 @@ public function get(string $key, ?string $context = null)
      * Save a value to the writable handler for later retrieval.
      *
      * @param mixed $value
-     *
-     * @return void
      */
-    public function set(string $key, $value = null, ?string $context = null)
+    public function set(string $key, $value = null, ?string $context = null): void
     {
         [$class, $property] = $this->prepareClassAndProperty($key);
 
@@ -90,10 +90,8 @@ public function set(string $key, $value = null, ?string $context = null)
      * Removes a setting from the persistent storage,
      * effectively returning the value to the default value
      * found in the config file, if any.
-     *
-     * @return void
      */
-    public function forget(string $key, ?string $context = null)
+    public function forget(string $key, ?string $context = null): void
     {
         [$class, $property] = $this->prepareClassAndProperty($key);
 
@@ -105,10 +103,8 @@ public function forget(string $key, ?string $context = null)
     /**
      * Removes all settings from the persistent storage,
      * Useful during testing. Use with caution.
-     *
-     * @return void
      */
-    public function flush()
+    public function flush(): void
     {
         foreach ($this->getWriteHandlers() as $handler) {
             $handler->flush();
diff --git a/tests/Commands/ClearSettingsTest.php b/tests/Commands/ClearSettingsTest.php
index a0d88b0..96b3e69 100644
--- a/tests/Commands/ClearSettingsTest.php
+++ b/tests/Commands/ClearSettingsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Commands;
 
 use CodeIgniter\Test\CIUnitTestCase;
@@ -28,7 +30,7 @@ protected function tearDown(): void
         CITestStreamFilter::removeErrorFilter();
     }
 
-    public function testSingleHandlerArray()
+    public function testSingleHandlerArray(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
@@ -46,7 +48,7 @@ public function testSingleHandlerArray()
         $this->assertStringContainsString('Settings cleared from array handler', $output);
     }
 
-    public function testSingleHandlerFile()
+    public function testSingleHandlerFile(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
@@ -64,7 +66,7 @@ public function testSingleHandlerFile()
         $this->assertStringContainsString('Settings cleared from file handler', $output);
     }
 
-    public function testMultipleHandlers()
+    public function testMultipleHandlers(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
@@ -82,7 +84,7 @@ public function testMultipleHandlers()
         $this->assertStringContainsString('Settings cleared from array and file handlers', $output);
     }
 
-    public function testThreeHandlers()
+    public function testThreeHandlers(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
@@ -100,7 +102,7 @@ public function testThreeHandlers()
         $this->assertStringContainsString('file handler', $output);
     }
 
-    public function testNoWriteableHandlers()
+    public function testNoWriteableHandlers(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
@@ -118,7 +120,7 @@ public function testNoWriteableHandlers()
         $this->assertStringContainsString('No handlers available to clear', $output);
     }
 
-    public function testEmptyHandlersArray()
+    public function testEmptyHandlersArray(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
@@ -135,7 +137,7 @@ public function testEmptyHandlersArray()
         $this->assertStringContainsString('No handlers available to clear', $output);
     }
 
-    public function testUserCancelsOperation()
+    public function testUserCancelsOperation(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("n\n"); // User answers 'n' to prompt
@@ -154,7 +156,7 @@ public function testUserCancelsOperation()
         $this->assertStringNotContainsString('Settings cleared', $output);
     }
 
-    public function testUserConfirmsOperation()
+    public function testUserConfirmsOperation(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n"); // User answers 'y' to prompt
@@ -173,21 +175,21 @@ public function testUserConfirmsOperation()
         $this->assertStringContainsString('Settings cleared from array handler', $output);
     }
 
-    public function testActuallyFlushesSettings()
+    public function testActuallyFlushesSettings(): void
     {
         PhpStreamWrapper::register();
         PhpStreamWrapper::setContent("y\n");
 
+        // Configure handler before getting service
+        $config           = config('Settings');
+        $config->handlers = ['array'];
+
         // Set some settings
         $settings = service('settings');
         $settings->set('Example.siteName', 'Test');
 
         $this->assertSame('Test', $settings->get('Example.siteName'));
 
-        // Run clear command
-        $config           = config('Settings');
-        $config->handlers = ['array'];
-
         command('settings:clear');
 
         PhpStreamWrapper::restore();
diff --git a/tests/DatabaseHandlerTest.php b/tests/DatabaseHandlerTest.php
index 80be565..d55836a 100644
--- a/tests/DatabaseHandlerTest.php
+++ b/tests/DatabaseHandlerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use CodeIgniter\I18n\Time;
@@ -24,11 +26,6 @@ final class DatabaseHandlerTest extends TestCase
      */
     protected $table;
 
-    /**
-     * @var string
-     */
-    protected $group;
-
     /**
      * Ensures we are using the database handler.
      */
@@ -42,7 +39,6 @@ protected function setUp(): void
 
         $this->settings = new Settings($config);
         $this->table    = $config->database['table'];
-        $this->group    = $config->database['group'];
     }
 
     /**
@@ -69,7 +65,7 @@ private function persistDeferredWrites(Settings $settings): void
         $handlers['database']->persistPendingProperties();
     }
 
-    public function testSetInsertsNewRows()
+    public function testSetInsertsNewRows(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
 
@@ -81,7 +77,7 @@ public function testSetInsertsNewRows()
         ]);
     }
 
-    public function testInvalidGroup()
+    public function testInvalidGroup(): void
     {
         $this->expectException(InvalidArgumentException::class);
 
@@ -95,7 +91,7 @@ public function testInvalidGroup()
         $this->settings->set('Example.siteName', true);
     }
 
-    public function testSetDefaultGroup()
+    public function testSetDefaultGroup(): void
     {
         /** @var \CodeIgniter\Settings\Config\Settings $config */
         $config                    = config('Settings');
@@ -114,7 +110,7 @@ public function testSetDefaultGroup()
         $this->assertTrue($this->settings->get('Example.siteName'));
     }
 
-    public function testSetInsertsBoolTrue()
+    public function testSetInsertsBoolTrue(): void
     {
         $this->settings->set('Example.siteName', true);
 
@@ -128,7 +124,7 @@ public function testSetInsertsBoolTrue()
         $this->assertTrue($this->settings->get('Example.siteName'));
     }
 
-    public function testSetInsertsBoolFalse()
+    public function testSetInsertsBoolFalse(): void
     {
         $this->settings->set('Example.siteName', false);
 
@@ -142,7 +138,7 @@ public function testSetInsertsBoolFalse()
         $this->assertFalse($this->settings->get('Example.siteName'));
     }
 
-    public function testSetInsertsNull()
+    public function testSetInsertsNull(): void
     {
         $this->settings->set('Example.siteName', null);
 
@@ -156,7 +152,7 @@ public function testSetInsertsNull()
         $this->assertNull($this->settings->get('Example.siteName'));
     }
 
-    public function testSetInsertsArray()
+    public function testSetInsertsArray(): void
     {
         $data = ['foo' => 'bar'];
         $this->settings->set('Example.siteName', $data);
@@ -171,7 +167,7 @@ public function testSetInsertsArray()
         $this->assertSame($data, $this->settings->get('Example.siteName'));
     }
 
-    public function testSetInsertsObject()
+    public function testSetInsertsObject(): void
     {
         $data = (object) ['foo' => 'bar'];
         $this->settings->set('Example.siteName', $data);
@@ -186,7 +182,7 @@ public function testSetInsertsObject()
         $this->assertSame((array) $data, (array) $this->settings->get('Example.siteName'));
     }
 
-    public function testSetUpdatesExistingRows()
+    public function testSetUpdatesExistingRows(): void
     {
         $this->hasInDatabase($this->table, [
             'class'      => 'Tests\Support\Config\Example',
@@ -205,7 +201,7 @@ public function testSetUpdatesExistingRows()
         ]);
     }
 
-    public function testWorksWithoutConfigClass()
+    public function testWorksWithoutConfigClass(): void
     {
         $this->settings->set('Nada.siteName', 'Bar');
 
@@ -218,7 +214,7 @@ public function testWorksWithoutConfigClass()
         $this->assertSame('Bar', $this->settings->get('Nada.siteName'));
     }
 
-    public function testForgetSuccess()
+    public function testForgetSuccess(): void
     {
         $this->hasInDatabase($this->table, [
             'class'      => 'Tests\Support\Config\Example',
@@ -236,7 +232,7 @@ public function testForgetSuccess()
         ]);
     }
 
-    public function testForgetWithNoStoredRecord()
+    public function testForgetWithNoStoredRecord(): void
     {
         $this->settings->forget('Example.siteName');
 
@@ -246,7 +242,7 @@ public function testForgetWithNoStoredRecord()
         ]);
     }
 
-    public function testFlush()
+    public function testFlush(): void
     {
         // Default value in the config file
         $this->assertSame('Settings Test', $this->settings->get('Example.siteName'));
@@ -267,7 +263,7 @@ public function testFlush()
         $this->assertSame('Settings Test', $this->settings->get('Example.siteName'));
     }
 
-    public function testSetWithContext()
+    public function testSetWithContext(): void
     {
         $this->settings->set('Example.siteName', 'Banana', 'environment:test');
 
@@ -283,7 +279,7 @@ public function testSetWithContext()
     /**
      * @see https://github.com/codeigniter4/settings/issues/20
      */
-    public function testSetUpdatesContextOnly()
+    public function testSetUpdatesContextOnly(): void
     {
         $this->settings->set('Example.siteName', 'Humpty');
         $this->settings->set('Example.siteName', 'Jack', 'context:male');
@@ -314,7 +310,7 @@ public function testSetUpdatesContextOnly()
         ]);
     }
 
-    public function testDeferredWritesReducesDatabaseQueries()
+    public function testDeferredWritesReducesDatabaseQueries(): void
     {
         // Create new settings instance with deferred writes enabled
         $deferredSettings = $this->createDeferredSettings();
@@ -362,7 +358,7 @@ public function testDeferredWritesReducesDatabaseQueries()
         ]);
     }
 
-    public function testDeferredWritesForgetDeletesAfterPersist()
+    public function testDeferredWritesForgetDeletesAfterPersist(): void
     {
         // First, insert a record to delete
         $this->settings->set('Example.siteName', 'InitialValue');
@@ -395,7 +391,7 @@ public function testDeferredWritesForgetDeletesAfterPersist()
         ]);
     }
 
-    public function testDeferredWritesDeleteThenSet()
+    public function testDeferredWritesDeleteThenSet(): void
     {
         // First, insert a record
         $this->settings->set('Example.siteName', 'InitialValue');
@@ -431,7 +427,7 @@ public function testDeferredWritesDeleteThenSet()
         ]);
     }
 
-    public function testNoDuplicatesWhenUpdatingExistingRecords()
+    public function testNoDuplicatesWhenUpdatingExistingRecords(): void
     {
         // Pre-populate database with existing records
         $this->settings->set('Example.siteName', 'InitialValue1');
@@ -493,7 +489,7 @@ public function testNoDuplicatesWhenUpdatingExistingRecords()
         ]);
     }
 
-    public function testNoDuplicatesWithMixedNewAndExistingRecords()
+    public function testNoDuplicatesWithMixedNewAndExistingRecords(): void
     {
         // Pre-populate database with some existing records
         $this->settings->set('Example.siteName', 'ExistingValue');
diff --git a/tests/FileHandlerTest.php b/tests/FileHandlerTest.php
index 5aab11e..503846c 100644
--- a/tests/FileHandlerTest.php
+++ b/tests/FileHandlerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use CodeIgniter\Settings\Config\Settings as ConfigSettings;
@@ -77,13 +79,13 @@ private function persistDeferredWrites(Settings $settings): void
         $handlers['file']->persistPendingProperties();
     }
 
-    public function testSetCreatesDirectory()
+    public function testSetCreatesDirectory(): void
     {
         $this->assertDirectoryExists($this->path);
         $this->assertIsWritable($this->path);
     }
 
-    public function testSetCreatesFile()
+    public function testSetCreatesFile(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
 
@@ -92,49 +94,49 @@ public function testSetCreatesFile()
         $this->assertStringEndsWith('.php', $files[0]);
     }
 
-    public function testSetStoresString()
+    public function testSetStoresString(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
 
         $this->assertSame('Foo', $this->settings->get('Example.siteName'));
     }
 
-    public function testSetStoresBoolTrue()
+    public function testSetStoresBoolTrue(): void
     {
         $this->settings->set('Example.siteName', true);
 
         $this->assertTrue($this->settings->get('Example.siteName'));
     }
 
-    public function testSetStoresBoolFalse()
+    public function testSetStoresBoolFalse(): void
     {
         $this->settings->set('Example.siteName', false);
 
         $this->assertFalse($this->settings->get('Example.siteName'));
     }
 
-    public function testSetStoresNull()
+    public function testSetStoresNull(): void
     {
         $this->settings->set('Example.siteName', null);
 
         $this->assertNull($this->settings->get('Example.siteName'));
     }
 
-    public function testSetStoresInteger()
+    public function testSetStoresInteger(): void
     {
         $this->settings->set('Example.siteName', 42);
 
         $this->assertSame(42, $this->settings->get('Example.siteName'));
     }
 
-    public function testSetStoresFloat()
+    public function testSetStoresFloat(): void
     {
         $this->settings->set('Example.siteName', 3.14);
 
-        $this->assertSame(3.14, $this->settings->get('Example.siteName'));
+        $this->assertEqualsWithDelta(3.14, $this->settings->get('Example.siteName'), PHP_FLOAT_EPSILON);
     }
 
-    public function testSetStoresArray()
+    public function testSetStoresArray(): void
     {
         $data = ['foo' => 'bar', 'baz' => 'qux'];
         $this->settings->set('Example.siteName', $data);
@@ -142,7 +144,7 @@ public function testSetStoresArray()
         $this->assertSame($data, $this->settings->get('Example.siteName'));
     }
 
-    public function testSetStoresObject()
+    public function testSetStoresObject(): void
     {
         $data = (object) ['foo' => 'bar'];
         $this->settings->set('Example.siteName', $data);
@@ -151,7 +153,7 @@ public function testSetStoresObject()
         $this->assertSame((array) $data, (array) $result);
     }
 
-    public function testSetUpdatesExistingValue()
+    public function testSetUpdatesExistingValue(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
         $this->assertSame('Foo', $this->settings->get('Example.siteName'));
@@ -164,19 +166,19 @@ public function testSetUpdatesExistingValue()
         $this->assertCount(1, $files);
     }
 
-    public function testGetNonExistentReturnsNull()
+    public function testGetNonExistentReturnsNull(): void
     {
         $this->assertNull($this->settings->get('Example.nonExistent'));
     }
 
-    public function testWorksWithoutConfigClass()
+    public function testWorksWithoutConfigClass(): void
     {
         $this->settings->set('Nada.siteName', 'Bar');
 
         $this->assertSame('Bar', $this->settings->get('Nada.siteName'));
     }
 
-    public function testForgetRemovesValue()
+    public function testForgetRemovesValue(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
         $this->assertSame('Foo', $this->settings->get('Example.siteName'));
@@ -187,7 +189,7 @@ public function testForgetRemovesValue()
         $this->assertSame('Settings Test', $this->settings->get('Example.siteName'));
     }
 
-    public function testForgetWithNoStoredRecord()
+    public function testForgetWithNoStoredRecord(): void
     {
         // Should not throw an exception
         $this->settings->forget('Example.siteName');
@@ -196,7 +198,7 @@ public function testForgetWithNoStoredRecord()
         $this->assertSame('Settings Test', $this->settings->get('Example.siteName'));
     }
 
-    public function testFlushRemovesAllFiles()
+    public function testFlushRemovesAllFiles(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
         $this->settings->set('Example.siteEmail', 'test@example.com');
@@ -213,7 +215,7 @@ public function testFlushRemovesAllFiles()
         $this->assertSame('Settings Test', $this->settings->get('Example.siteName'));
     }
 
-    public function testFlushRemovesFilesAndContextDirectories()
+    public function testFlushRemovesFilesAndContextDirectories(): void
     {
         // Create files in main directory (null context)
         $this->settings->set('Example.siteName', 'Main');
@@ -243,14 +245,14 @@ public function testFlushRemovesFilesAndContextDirectories()
         $this->assertSame('Settings Test', $this->settings->get('Example.siteName', 'production'));
     }
 
-    public function testSetWithContext()
+    public function testSetWithContext(): void
     {
         $this->settings->set('Example.siteName', 'Banana', 'environment:test');
 
         $this->assertSame('Banana', $this->settings->get('Example.siteName', 'environment:test'));
     }
 
-    public function testSetUpdatesContextOnly()
+    public function testSetUpdatesContextOnly(): void
     {
         $this->settings->set('Example.siteName', 'Humpty');
         $this->settings->set('Example.siteName', 'Jack', 'context:male');
@@ -262,7 +264,7 @@ public function testSetUpdatesContextOnly()
         $this->assertSame('Jane', $this->settings->get('Example.siteName', 'context:female'));
     }
 
-    public function testContextFallsBackToGeneral()
+    public function testContextFallsBackToGeneral(): void
     {
         $this->settings->set('Example.siteName', 'General');
 
@@ -270,7 +272,7 @@ public function testContextFallsBackToGeneral()
         $this->assertSame('General', $this->settings->get('Example.siteName', 'context:nonexistent'));
     }
 
-    public function testMultiplePropertiesInSameFile()
+    public function testMultiplePropertiesInSameFile(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
         $this->settings->set('Example.siteEmail', 'test@example.com');
@@ -283,7 +285,7 @@ public function testMultiplePropertiesInSameFile()
         $this->assertCount(1, $files);
     }
 
-    public function testDifferentClassesCreateDifferentFiles()
+    public function testDifferentClassesCreateDifferentFiles(): void
     {
         $this->settings->set('Example.siteName', 'Foo');
         $this->settings->set('Nada.siteName', 'Bar');
@@ -296,7 +298,7 @@ public function testDifferentClassesCreateDifferentFiles()
         $this->assertCount(2, $files);
     }
 
-    public function testPersistenceAcrossInstances()
+    public function testPersistenceAcrossInstances(): void
     {
         // Set value in first instance
         $this->settings->set('Example.siteName', 'Persistent');
@@ -312,7 +314,7 @@ public function testPersistenceAcrossInstances()
         $this->assertSame('Persistent', $newSettings->get('Example.siteName'));
     }
 
-    public function testFileContentIsValidPHP()
+    public function testFileContentIsValidPHP(): void
     {
         $this->settings->set('Example.siteName', 'Test');
 
@@ -321,6 +323,8 @@ public function testFileContentIsValidPHP()
 
         $content = file_get_contents($files[0]);
 
+        $this->assertIsString($content);
+
         // Should start with PHP tag
         $this->assertStringStartsWith('<?php', $content);
 
@@ -332,7 +336,7 @@ public function testFileContentIsValidPHP()
         $this->assertIsArray($data);
     }
 
-    public function testUsesClassNameForFilename()
+    public function testUsesClassNameForFilename(): void
     {
         $this->settings->set('Example.siteName', 'Test');
 
@@ -342,7 +346,7 @@ public function testUsesClassNameForFilename()
         $this->assertFileExists($expectedFile);
     }
 
-    public function testContextUsesHashedSubdirectory()
+    public function testContextUsesHashedSubdirectory(): void
     {
         $context = 'environment:production';
         $this->settings->set('Example.siteName', 'Prod', $context);
@@ -354,7 +358,7 @@ public function testContextUsesHashedSubdirectory()
         $this->assertFileExists($expectedFile);
     }
 
-    public function testEmptyStringContextIsDifferentFromNull()
+    public function testEmptyStringContextIsDifferentFromNull(): void
     {
         // Set with null context
         $this->settings->set('Example.siteName', 'Null', null);
@@ -376,7 +380,7 @@ public function testEmptyStringContextIsDifferentFromNull()
         $this->assertSame('Empty', $this->settings->get('Example.siteName', ''));
     }
 
-    public function testConcurrentReadsDontLoadFileTwice()
+    public function testConcurrentReadsDontLoadFileTwice(): void
     {
         $this->settings->set('Example.siteName', 'Test');
         $this->settings->set('Example.siteEmail', 'test@example.com');
@@ -395,7 +399,7 @@ public function testConcurrentReadsDontLoadFileTwice()
         $this->assertSame('test@example.com', $value2);
     }
 
-    public function testHasReturnsTrueWhenValueExists()
+    public function testHasReturnsTrueWhenValueExists(): void
     {
         $this->settings->set('Example.siteName', 'Test');
 
@@ -407,7 +411,7 @@ public function testHasReturnsTrueWhenValueExists()
         $this->assertTrue($handlers['file']->has('Tests\Support\Config\Example', 'siteName'));
     }
 
-    public function testHasReturnsFalseWhenValueDoesNotExist()
+    public function testHasReturnsFalseWhenValueDoesNotExist(): void
     {
         $reflection       = new ReflectionClass($this->settings);
         $handlersProperty = $reflection->getProperty('handlers');
@@ -420,7 +424,7 @@ public function testHasReturnsFalseWhenValueDoesNotExist()
      * Simulate writes from different PHP processes (each with separate in-memory state)
      * by manually modifying the file between operations
      */
-    public function testMergesChangesFromDifferentProcesses()
+    public function testMergesChangesFromDifferentProcesses(): void
     {
         // Process A writes siteName
         $this->settings->set('Example.siteName', 'First');
@@ -457,7 +461,7 @@ public function testMergesChangesFromDifferentProcesses()
         $this->assertSame('Second', $newSettings->get('Example.siteTitle'));
     }
 
-    public function testDeferredWritesReducesFileWrites()
+    public function testDeferredWritesReducesFileWrites(): void
     {
         // Create new settings instance with deferred writes enabled
         $deferredSettings = $this->createDeferredSettings();
@@ -488,7 +492,7 @@ public function testDeferredWritesReducesFileWrites()
         $this->assertSame('Value3', $data['siteTitle']['value']);
     }
 
-    public function testDeferredWritesForgetDeletesAfterPersist()
+    public function testDeferredWritesForgetDeletesAfterPersist(): void
     {
         // First, create a file with a value
         $this->settings->set('Example.siteName', 'InitialValue');
@@ -525,7 +529,7 @@ public function testDeferredWritesForgetDeletesAfterPersist()
         $this->assertArrayNotHasKey('siteName', $data);
     }
 
-    public function testDeferredWritesDeleteThenSet()
+    public function testDeferredWritesDeleteThenSet(): void
     {
         // First, create a file with a value
         $this->settings->set('Example.siteName', 'InitialValue');
diff --git a/tests/HelperTest.php b/tests/HelperTest.php
index 9ac17ea..e2183e8 100644
--- a/tests/HelperTest.php
+++ b/tests/HelperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use CodeIgniter\Settings\Settings;
@@ -20,12 +22,12 @@ protected function setUp(): void
         helper(['setting']);
     }
 
-    public function testReturnsServiceByDefault()
+    public function testReturnsServiceByDefault(): void
     {
         $this->assertInstanceOf(Settings::class, setting());
     }
 
-    public function testThrowsExceptionWithInvalidField()
+    public function testThrowsExceptionWithInvalidField(): void
     {
         $this->expectException('InvalidArgumentException');
         $this->expectExceptionMessage('$key must contain both the class and field name, i.e. Foo.bar');
@@ -33,7 +35,7 @@ public function testThrowsExceptionWithInvalidField()
         setting('Foobar');
     }
 
-    public function testSetsNull()
+    public function testSetsNull(): void
     {
         setting('Foo.bam', null);
 
@@ -41,14 +43,14 @@ public function testSetsNull()
         $this->assertNull(setting('Foo.bam'));
     }
 
-    public function testReturnsValueDotArray()
+    public function testReturnsValueDotArray(): void
     {
         service('settings')->set('Foo.bar', 'baz');
 
         $this->assertSame('baz', setting('Foo.bar'));
     }
 
-    public function testSettingValueDotArray()
+    public function testSettingValueDotArray(): void
     {
         service('settings')->set('Foo.bar', 'baz');
 
diff --git a/tests/SettingsTest.php b/tests/SettingsTest.php
index a519142..577ab87 100644
--- a/tests/SettingsTest.php
+++ b/tests/SettingsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use CodeIgniter\Settings\Settings;
@@ -11,7 +13,7 @@
  */
 final class SettingsTest extends TestCase
 {
-    public function testSettingsUsesParameter()
+    public function testSettingsUsesParameter(): void
     {
         $config           = config('Settings');
         $config->handlers = [];
@@ -22,7 +24,7 @@ public function testSettingsUsesParameter()
         $this->assertSame([], $result);
     }
 
-    public function testServiceUsesConfig()
+    public function testServiceUsesConfig(): void
     {
         Services::resetSingle('settings');
 
@@ -35,17 +37,17 @@ public function testServiceUsesConfig()
         $this->assertSame([], $result);
     }
 
-    public function testSettingsGetsFromConfig()
+    public function testSettingsGetsFromConfig(): void
     {
         $this->assertSame(config('Example')->siteName, $this->settings->get('Example.siteName'));
     }
 
-    public function testSettingsNotFound()
+    public function testSettingsNotFound(): void
     {
         $this->assertSame(config('Example')->siteName, $this->settings->get('Example.siteName'));
     }
 
-    public function testGetWithContext()
+    public function testGetWithContext(): void
     {
         $this->settings->set('Example.siteName', 'NoContext');
         $this->settings->set('Example.siteName', 'YesContext', 'testing:true');
@@ -54,14 +56,14 @@ public function testGetWithContext()
         $this->assertSame('YesContext', $this->settings->get('Example.siteName', 'testing:true'));
     }
 
-    public function testGetWithoutContextUsesGlobal()
+    public function testGetWithoutContextUsesGlobal(): void
     {
         $this->settings->set('Example.siteName', 'NoContext');
 
         $this->assertSame('NoContext', $this->settings->get('Example.siteName', 'testing:true'));
     }
 
-    public function testForgetWithContext()
+    public function testForgetWithContext(): void
     {
         $this->settings->set('Example.siteName', 'Bar');
         $this->settings->set('Example.siteName', 'Amnesia', 'category:disease');
diff --git a/tests/_support/Config/Example.php b/tests/_support/Config/Example.php
index e0137c8..f98bbce 100644
--- a/tests/_support/Config/Example.php
+++ b/tests/_support/Config/Example.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support\Config;
 
 use CodeIgniter\Config\BaseConfig;
diff --git a/tests/_support/TestCase.php b/tests/_support/TestCase.php
index ad11f40..2f66b56 100644
--- a/tests/_support/TestCase.php
+++ b/tests/_support/TestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support;
 
 use CodeIgniter\CLI\CLI;